15364-55-3Relevant articles and documents
Integrating reaction and analysis: Investigation of higher-order reactions by cryogenic trapping
Stockinger, Skrollan,Trapp, Oliver
, p. 1837 - 1842 (2013/10/22)
A new approach for the investigation of a higher-order reaction by on-column reaction gas chromatography is presented. The reaction and the analytical separation are combined in a single experiment to investigate the Diels-Alder reaction of benzenediazonium-2-carboxylate as a benzyne precursor with various anthracene derivatives, i.e. anthracene, 9-bromoanthracene, 9-anthracenecarbox-aldehyde and 9-anthracenemethanol. To overcome limitations of short reaction contact times at elevated temperatures a novel experimental setup was developed involving a cooling trap to achieve focusing and mixing of the reactants at a defined spot in a fused-silica capillary. This trap functions as a reactor within the separation column in the oven of a gas chromatograph. The reac-tants are sequentially injected to avoid undefined mixing in the injection port. An experimental protocol was developed with optimized injection intervals and cooling times to achieve sufficient conversions at short reaction times. Reaction products were rapidly identified by mass spectrometric detection. This new approach represents a practical procedure to investigate higher-order reactions at an analytical level and it simultaneously provides valuable information for the optimization of the reaction conditions.
Nucleophilic substitution induced by electron transfer at the bridgehead of polycyclic alkanes: Competition between polar and radical pathways
Adcock,Clark,Trout
, p. 3362 - 3371 (2007/10/03)
A series of 2,5(or 1,4)-dihaloadamantanes (4 and 5, X = Y = halogens) and 9,10-dihalotriptycenes (7, X = Y = halogens) as well as two 5-halo (X) adamantan-2-ones (6, Y = O,X = Br and I) have been treated with Me3SnLi in THF in the absence and presence of tert-butylamine (TBA) and dicyclohexylphosphine (DCHP). The product distributions of these reactions have been established by 13C and 119Sn NMR spectroscopy, vapor-phase chromatographic analyses, and GC/MS. The former compounds (4 and 5) appear to react exclusively by a free-radical chain process (SRN1 mechanism) to yield tin substitution products. By contrast, the triptycenes react predominantly by a polar mechanism initiated by the formation of a carbanion. In the case of the halo ketones (6, Y = O,X = Br and I), a mechanistic divergence of the reaction was unexpectedly encountered. Whereas the bromo ketone provides the substitution product (6, Y = O,X = SnMe3) in good yield (ca. 75%), apparently by a radical pathway, the iodo ketone yields a fragmentation product (ca. 95% yield) by a polar mechanism. This mechanistic switch highlights the importance of the electronegativity of the leaving group as well as substituent-induced electron delocalization as molecular factors governing the competition between radical and polar pathways.
Transmission of Polar Substituent Effects through the Bicyclooctane Ring System as Monitored by 19F NMR Shifts: A 19F NMR Study of 10-Substituted 9-Fluorotriptycenes and 4-Substituted 4'-Fluorobibicyclooctanes
Adcock, William,Iyer, V. Sankar
, p. 5259 - 5266 (2007/10/02)
A series of 10-substituted 9-fluorotriptycenes (5) encompassing a wide range of substituents has been synthesized and characterized, and the 19F chemicql shifts have been measured in several solvents.Multiple linear regression analysis reveals no discernible relationship between the 19F substituent chemical shifts (SCS) of 5 and polar substituent constants.Comparisons have been made between 5 and corresponding 4-substituted bicyclooct-1-yl fluorides (1), which strongly corroborate the previous interpretation of the 19F SCS of the latter system.In particular, the "through-bond" nature of the strong electronegativity effect (?x) in 1 seems established.A more restricted series of 4-substituted 4'-fluorobibicyclooctanes (6) have been acquired, and the pattern of shifts has been found to parallel polar field constants (?F values).In contrast to 1, no evidence for a significant ?x effect is apparent in 6.The pronounced sensitivity of 6 to electric field effects prompted its use in the determination of an unequivocal ?F value for the CH3 group.
High-Yield Direct Synthesis of a New Class of Tertiary Organolithium Derivatives of Polycyclic Hydrocarbons
Molle, G.,Bauer, P.,Dubois, J. E.
, p. 2975 - 2981 (2007/10/02)
For the first time, 1- and 2-adamantyllithium, 1-diamantyllithium, 3,5,7-trimethyl-1-adamantyllithium, 1-twistyllithium, 3-methyl-7-noradamantyllithium, 1-triptycyllithium, and 3-homoadamantyllithium have been directly synthesized from the reaction of an organic halide and lithium metal.By use of certain experimental parameters, the phenomena at the metal-solution interface are controlled, thereby resulting in exceptionally high yields of this new class of organometallic compounds (>75percent, except in the case of 3-homoadamantyllithium).Competition between formation of the organometallic compound and formation of solvent-attack byproducts is determined by the degree of adsorption of the transient species (anion radical RX-. or radical pair R..Li) generated at the metal surface during attack by the halogenated derivative.
